Which type of metals can be detected using a magnet?

Ferrous metals are distinguished by their iron content, which gives them magnetic properties. When a magnet is brought near ferrous metals—such as iron, cobalt, and nickel—they are attracted due to the alignment of their magnetic domains. This characteristic allows for easy detection using magnetic fields, making ferrous metals significantly different from non-ferrous metals, which do not possess magnetic properties and are not attracted to magnets.

Other metal categories mentioned in the choices, such as alkali metals and noble metals, are also not ferrous and therefore do not exhibit magnetic attraction. Alkali metals primarily consist of highly reactive metals like lithium and sodium, while noble metals like gold, silver, and platinum are known for their resistance to corrosion and oxidation, as well as their non-magnetic nature. Hence, ferrous metals are the only group that can be reliably detected using a magnet.